Navigation for Transcranial Magnetic Stimulation

© Photo Fraunhofer FIT

Some scientists expect that transcranial magnetic stimulation (TMS) may in the future help to treat severe depressive disorders.

TMS uses a pulsating magnetic field to selectively stimulate specific brain regions. Today, it is used to explore processes inside the brain, in order to understand motor and sensory functions, visual information processing, speech functions, learning and memory as well as emotional aspects of the brain.

Accurate positioning of the coil that generates the magnetic field is crucial for producing significant results. Here the navigation system TMSNavigator developed by LOCALITE GmbH, Bonn, provides significant support for the neurologist. It tracks the position of the TMS coil by a camera system and displays the coil position in previously acquired magnetic resonance images. This enables the neurologist to accurately position the TMS coil against the head of the patient and to aim the magnetic field at the target area inside the brain.

Fraunhofer FIT developed the visualization software for the TMSNavigator. It displays anatomical structures and functional regions of the brain (e.g., visual cortex, speech center) in a three dimensional view.

Based on automatic recognition of the brain in magnetic resonance imaging data (segmentation), irrelevant structures, e.g. the skull, can be faded out on request. The direct view on the brain surface enables the neurologist to use the anatomical structures of the brain surface (gyri and sulci) for orientation.

Supporting a geometric alignment (registration) of the data sets, the visualization software lets the neurologist combine the morphological image data with functional magnetic resonance imaging. Relevant functional areas of the brain can thus be displayed as a colored overlay of the brain surface.

The visualization software was successfully tested in co-operation with the TMS Laboratory of the University Hospital Aachen.

Overlaid presentation of morphological and functional magnetic resonance image data in three orthogonal 2D slices and a 3D view of the brain surface.